Treating chilled cast-iron car-wheels



UNITED STATES PATENT @EETQE.

WVILLIAM IV. LOBDELL, OF WILMINGTON, DELAWARE.

TREATING CHILLED CAST-IRON CAR-WHEELS, ROLLS, 84.0.

SPECIFICATION forming part of Letters Patent No. 615,075, dated November29, 1898.

Ap lication filed November 28, 1892. Serial No. 453,402. (No specimens.)

T0 aZZ whom it may concern.-

Be it known that I, WILLIAM W. LOBDELL, a citizen of the United States,and a resident of Wilmington, Delaware, have invented certainImprovements in Treating Chilled Cast- Iron Car -Wheels, Rolls, &c., ofwhich the following is a specification.

The object of my invention is to so treat chilled cast-iron wheels,rolls, and the like as to relieve them from defects which arise from thechilling operation; and this object I attain in the manner hereinafterset forth.

In casting chilled iron car-wheels the tread of the wheel is castagainst a chill which is made of iron or other metal that is a goodconductor of heat, the sides, plates, or spokes of the wheel being castin sand.

Rapid transmission of heat from the molten iron through the chillagainst which it is cast causes the tread of the wheel to present anentirely different physical structure from that portion of the wheelwhich is cast against the sand, the chilled portion being crystalline incharacter and silvery white in color, while the other portions of thewheel are of the ordinary color and character of cast-iron.

Because of the rapid transmission of heat from the tread of the wheelthat portion of the wheel cools and contracts rapidly, while the hub orcentralportion still remains in a semifluid state. This causes a strainupon the wheel, which is partially relieved by removing the wheels fromthe molds as soon as set and covering them up in sand or placing them inair-tight pits, where they are allowed to cool slowly; but'that thisstrain is not entirely removed by such treatment is evidenced by thefact that if two thirty-three-inch wheels are cast from the same patternand from the same ladle of iron, one in a chill-mold and the other in asand mold, the one cast in the sand will be larger in diameter, probablyby.

one-fourth or one-third of an inch, than the one cast in the chill-mold,and when such wheels are subjected to a breaking test the one cast inthe sand mold will be much the stronger of the two. This indicates thatthe process of casting the chilled wheel causes.

more than a normal shrinkage of the iron.

Of course a wheel may be weak because of the use of iron of inferiorquality; but chilled wheels, even if made of iron of the best qualingthe chill or wearing part of the tread; in

fact, they may be permanently expanded to an extent greater than thedifference between a wheel cast in a chill and one cast in sand, thusindicating that the process not only relieves the casting from itsabnormal shrinkage, but from the ordinary shrinkage, or may even havethe effect of permanently expandingthecastingbeyonditsnormal limits. Thetreatment seems to effect some change in the physical or molecularstructure of the iron in the plates and hub of the wheel, the iron inthese parts of the wheel being changed from a light gray to abluish-black color and partaking more of afibrous nature than of theusual granular form of cast-iron-that is to say, the crystals or grainsare enlarged and interlaced and the casting is of greater bulk, greatertoughness, and of greatly-increased strength as compared with the samecasting before treatmentand this is true not only of wheels cast in achill, but also of those cast in asand mold, there being in either casea great increase in the strength of the wheel, this increase varyingfrom one hundred to five hundred'per cent. or more and being generallyinproportion to the degree of perma .nent expansion or increase in bulk ofthe 2.0455 per cent, and combined carbon, 1.2008 per cent.

This analysis shows that the total carbon in specimen No. 1 was 3.1087percent. and in specimen No. 2, 3.2523, showing an increase of totalcarbon of .0830 per cent, while the combined carbon has increased from1.0265 per cent. to 1.2008 per cent, showing an increase of .1803 percent, and in all cases the treated casting will show an increase intotal and combined carbon.

lVhile in some cases a mallcableiron casting, when fractured, may show abluish'black color, somewhat similar to that found in the unchilledportion of my castings, it should be observed that in addition to thefact that such malleable-iron castings are not composed of chilled andunehilled portions the change in total and combined carbon therein isradically different from that in my castings, because the total carbonin the malleable-iron castings is slightly decreased and the combinedcarbon is changed to the graphitic form.

I am aware that it has been proposed to take chilled car-wheels directlyfrom the molds as soon as they were set and to place such hot wheels inan annealing-kiln, in which they were heated to still higher temperatureor to a point a little below the point of fusion and then allowed tocool slowly; but this process is essentially different from that which Ihave devised, for in carrying out the latter process the wheels arefirst permitted to become quite cold and to have an abnormal shrinkageand are then gradually heated and gradually cooled, with the result ofpermanently i11- creasing their diameter and completely overcoming theobjections due to such abnormal shrinkage.

I am also aware of the patent of H. V. Moore, No. 51,338, dated December5, 1865, which describes a method of annealing chilled iron car-wheelsby superposing them while hot in a soaking-pit, packing the webs withcharcoal, and protecting the chilled rims from the effect of the heatdue to the slow combustion of such charcoal, the intention being tocause an approximation to malleable iron in the webs of the wheels. Suchtreatment does not heat the wheels uniformly throughout their entireextent, as in my process, and the wheel produced is essentiallydifferent from one ma spccordance with my process that is to say, itisnot permanently expanded, and the change in therarbon contents of themetal, if any there be, is intlle direction of an increase in graphiticcarbon instead of an increase in combined carbon.

The degree of temperature to which the wheels are subjected in carryingout my invention should not be so high as to inj uriously affect thechill, and the application of heat may be continued until the desiredexpansion of the article under treatment has been effected, the lengthof treatment varying, depending upon the bulk of said article and uponthe depth of chill. I may say, however, that in case of ordinarycar-wheels I prefer to heat them to a dark cherry red, the temperaturebeing from 900 to 1,200 Fahrenheit, the treatment being continued fortwenty-four hours or in some cases even longer in order to insure theproper permanent expansion of the casting.

The advantages of my improved process are, primarily, the very greatincrease in strength, and,furthcrmore,1he abilitytoproducewheels orother objects with an extra deep chill without impairment of strength,therebyinsuring greatly-increased wearing qualities and the ability touse grades of iron which will produce a very hard and lasting chilledsurface, which grades of iron, because of their great shrinkage, cannotnow be used with safety.

In the case of car-wheels treated in accordance with my invention theheating of the iron by friction due to long-continued action of thebrake cannot have the effect of expanding the Wheel so as to crack theplates of the same, because such heating cannot possibly be as great asthat which the Wheel receives in the carrying out of my improvedprocess; hence a fruitful source of loss and danger in the use ofordinary chilled carwheels is effectually overcome.

In the case of chilled rolls or other expensive chilled castings thegreat increase in strength and greater depth of chill renders them 111uoh more durable in use and decreases the risk of breakage.

Having thus described my invention, I claim and desire to secure byLetters Patent- 1. The mode herein described of treating chilledcastings, said mode consistingin first permitting said castings tobecome cold and then subjecting them, uniformly throughout their entireextent, to a temperature from about 900 to 1,200 Fahrenheit, whereby thecasting is permanently expanded without injuriously affecting the chill.

2. As a new article of manufacture, the herein-described iron casting,such as a carwheel or roll, composed of chilled and unchilled portions,possessing as physical characteristics in the unchilled portion abluishblack color, enlarged interlaced crystals or grains, greater bulkand toughness, much greater strength, and a greater percentage both oftotal carbon and combined carbon, than the same casting beforetreatment, substantially as specified.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

XVILLIAM IV. LOBDELL.

Witnesses:

CHAS. F. WoLLAsToN, WINFIELD T. MoKAIo.

